Quantum mechanics, Furry's hypothesis, and a measure of decoherence in the K 0 K̄ 0 system

We consider strangeness correlations of the Einstein-Podolski-Rosen type in ${K}^{0}{K}^{0}$ pairs created in a ${J}^{\mathrm{PC}}{=1}^{\ensuremath{-}\ensuremath{-}}$ state as a function of time under the hypothesis that spontaneous decoherence takes place. We parametrize the degree of decoherence by a factor $(1\ensuremath{-}\ensuremath{\zeta})$ which multiplies the quantum-mechanical interference terms occurring in the amplitudes for like and unlike strangeness events and discuss the dependence of this procedure on the basis chosen in ${K}^{0}\ensuremath{-}{K}^{0}$ space to which the interference terms correspond. Consequently, all statements about the ``decoherence parameter'' $\ensuremath{\zeta}$ inferred from experimental data are basis dependent as well. We illustrate this point by estimating the value of $\ensuremath{\zeta}$ for the two bases ${{K}_{L}{,K}_{S}}$ and ${{K}^{0},{K}^{0}}$ with the help of recent data of the CPLEAR experiment.